In some conventional systems, manufacturer specifications for equipment are published with maximum load ratings. As an example, for fixed speed HVAC (heating, ventilation, and air conditioning) pump systems, performance criteria may be based on a narrow band of conditions, optimizing for occupant use during maximum load, which often meant sacrificing operating efficiency during part-load conditions.
Prior to variable speed drives, some conventional industry practices meant designing heating, cooling and plumbing system performance around a single point that represented the most extreme conditions or loads that a building might experience during its operating lifecycle.
A difficulty with some existing systems is that, at part-load, the pumping system may be susceptible to instability, poor occupant comfort and energy and economic wastage.
The traditional selection of a pump or pumps may result in wastage of resources and inefficient operation. Load limits for a building may vary so that the variable speed equipment, (e.g. pump, boiler plant, booster or other) may not be required to operate at full capacity to service the system requirements. Further, improper equipment selection may require a repair or total replacement of the equipment to a more suitable size of equipment (e.g. pump, boiler plant, booster, or other).
Additional difficulties with existing systems may be appreciated in view of the detailed description below.